1. Field of the Invention
The present invention relates to a mounting assembly for mounting a heat sink to an electronic package mounted on a circuit board, and particularly to a mounting assembly which easily and securely mounts the heat sink to the electronic package.
2. The Related Art
A computer central processing unit (CPU) is the core administrator of electrical signals in most contemporary personal computers. Continued development of CPUs has enabled them to perform more and more functions. Heat generated by CPUs has increased commensurately. Measures must be taken to efficiently remove the heat from the CPU. Typically, a heat sink having great heat conductivity is mounted on the CPU to remove heat therefrom.
A conventional configuration for fastening a heat sink to a CPU comprises a plurality of barbs formed around a bottom of the heat sink. A plurality of protruding edges extends from a CPU connector that supports the CPU, for engaging with the barbs and thereby securing the heat sink to the CPU. However, this configuration necessitates unduly large force being applied to tightly press the heat sink onto the CPU. The CPU is liable to be damaged if excessively large force is applied during assembly, or if force is applied in an incorrect direction. Therefore assembly needs to be performed carefully and slowly. This is particularly inefficient in mass production facilities.
Accordingly, various clips have been developed for mounting a heat sink to a CPU. As shown in TW Patent No. 87221090, a conventional clip includes an H-shaped portion and four legs extending from four distal ends of the H-shaped portion respectively. A barb is formed at a distal end of each leg, for engaging in a corresponding hole around a CPU. However, this configuration may not apply sufficient force to securely fasten the heat sink on the surface of the CPU. In addition, the clip is prone to fatigue and deformation after prolonged use. Deformation further reduces the retaining force.
Accordingly, an object of the present invention is to provide a mounting assembly which easily and securely mounts a heat sink to an electronic package mounted on a circuit board.
To achieve the above object, a mounting assembly in accordance with a preferred embodiment of the present invention comprises a back plate, a clip and two screws. The back plate comprises a cross-shaped main body, and a pair of first positioning posts and a pair of second positioning posts extending upwardly from the main body. An annular groove is defined in a top end of each first positioning post. A threaded hole is vertically defined in each second positioning post. The clip comprises a horizontal portion, and a pair of first legs and a pair of second legs extending from the horizontal portion. A guiding hole and a positioning slot communicating with the guiding hole are defined in a distal end of each first leg. A fastening slot is defined in a distal end of each second leg. An electronic package such as a CPU is mounted on a top side of a circuit board. The back plate abuts an underside of the circuit board, and the clip and a heat sink are disposed at the top side of a circuit board. The positioning slots of the clip engagingly receive the first positioning posts of the back plate. The screws are inserted through the fastening slots of the clip into the corresponding threaded holes of the second positioning posts of the back plate. The mounting assembly thus secures the heat sink to the CPU.